Diastereodivergent Synthesis of α-Chiral Tertiary Azides through Catalytic Asymmetric Michael Addition

Abstract

A diastereodivergent synthesis of α-chiral tertiary azides through catalytic enantioselective Michael addition of α-azido indanones to β,γ-unsaturated α-ketoesters is described. The merger of a newly designed bifunctional phosphoramide C4b and hexafluoroisopropanol (HFIP) affords syn-adducts, whereas the use of thiourea C6a provides anti-adducts without the aid of HFIP. Notably, additive HFIP proves to be the key control element to achieve diastereoselectivity reversal in the former case. The products are readily converted to enantioenriched spiro N-heterocycles.